Method for improving the solubility of dyestuffs



' Patented Mar. 10, 1931 UNITED STATES PATENT OFFICE" ARTHUR R. MURPHY, 0F MILWAUKEE, AND JOSEPH B. OESCH, OF sou'rn: MILWAUKEE, WISCONSIN, ASSIGNQRS, BY MEsNE ASSIGNMENTS, T0 NEWPORT CHEMICAL 00R- PORATIO N, A CORPORATION OF DELAWARE METHOD FOR IMPROVING THE SOLUBILITY 0F DYESTUFFS 1 no Drawing.

This invention relates to a method forimproting the solubility of certain dyestufi's in the dyebath, with particular reference to those dyestuffs which tend to form insolu- 5 ble'lakes with impurities normally present in technical dyestuffs or present in the water of the dyebath. I

It is an object of this invention to provide a 'method for the ready solution in. the dye bath of colors which have a tendency to form insoluble precipitates when dilutedwith water and more especially when diluted with water having an appreciable hardness.

'It' is knownthat certain dyestuifs, even' sourceland to offset to a large degree the to variations in dyeing" caused by waters of different hardness, so that similar dyeing shades and efiiciency maybe expected regardless of the dyebath. 0 It is still a further object of this invention to provide a method of making up a stock solution of a dyestufi' in ordinary water so that the concentration of the dyestuifv in the stock solution will remain substantiallyhomo eneous. J

gther and further objects will become apparent-from disclosures in the specification and appended claims.

Heretofore known methods of avoiding 5 the difiiculties outlined above have employed the following aids to solution of the dyestufl. Certaln salts, as for example Glaubers salt, sodium carbonate, disodium phosphate and the like have been either mixed 0 with the vdyes ufi before dissolving in the,

type of water used in the- Application filed February 6, 1928. Serial No. 252,424.

dyebath or added to the dyebath itself previous to the'dis'solvi-ng of the'dyestufl. The added salts tend to remove the hardness properties of'the water, precipitating out the dissolved'calcium in the form of cal-. cium carbonate, calcium sulphate, calcium phosphate, or other insoluble calcium salt. In certain other cases, soaps have been employed for removing the hardness. By the use of the above methods, advantages are gained whereby many dyestuffs may be dissolved in an eflicient manner. However, in certain other cases, the above methods of treatment are entirely inadequate to perform the function. I i

We have discovered that the soluble pyrophosphate salts, particularly sodium pyrophosphate, when mixed with these dyestuffs or added to the dyebath previous to the addition of the dyestufi', react in a most unusual manner to effect clear solution of; the dyestuff in water. By using a pyrophosphate in this way, certain dyestuffs which could not be adequately dissolved in the dyebath by employing previously known methods, dissolve to clear solutions and pro duce level dyeings.

The nature of the specific reaction involved isunknown to us. It may be that the reac-' tion is due to the removal of the hardness of the water in the form of insoluble salts, such as calcium pyrophosphate However, when the results obtained by the use of sodium sulfate, sodium carbonate, disodium phosphate,

soap andthe like, which, as is known, form practically insoluble calcium salts, are compared, our theory does not seem toaccount for the remarkable difierences. It may be that the metals capable of forming lakes with the dye-stuffs enter into a complex combination with the pyrophosphate and in the ,combination are incapable of forming lakes with the respective dyestufis. A further explanation ofthe phenomena occurring in the dye? bath in conjunction with the use of pyrophosphate salts is that the lake of the dye stufi may actually be precipitated in a colloidal form, thereby escaping detection to the,

eye and for all practical purposes reacting as a true solution.

Notwithstanding the hypothetical nature of such theories, the fact remains that pyrowaters.

The following tabulated data and the examples will serve to illustrate further the invention. At the head of the columns are certain dyestufiswhich tend to form insoluble lakes with the impurities normally present in water, followed by the usual concentration of the dyestufi employed, to illustrate the use of pyrophosphate salts in effecting good solubility in water. The lake water referred to in the various experiments has a hardness corresponding to 125 parts per million. A water of thisdegree of hardness is considered a relatively hard water for use in making up .a dyebath. The amounts of salts used, as for example, sodium pyrophosphate, disodium phosphate, sodium carbonate and the like, correspond to three timesthe amount necessary to combine with the salts producing the hardness in the water; In'all these cases, the sodium pyrophosphate gave very satisfactory results, whereas the disodium phosphate and sodium carbonate gave results which show that they are totally unsuited for performing the function.

Congo Corinth .imrect mt Benzo Purpurin Color color index #375 ggggk g g 413, color index Concentration 1 gr./200 00.1120 0.2gr./200cc. H10 1gr./1000 cc.HzO

Solubility Distilled'water. Very slight pre- Clear Clear solution.

' cipitate.

4 Lakewater Heavy precipi- Heavy precipi- Slight precipitate. v tate. ftate.

Lake fwater Practically Very slight pre- Clear solution. with sodium clear. cipitate cold, pyrophoscompletely phate. soluble hot.

' Lake water Heavy precipi- Heavy prec ipi- Sli ht reci iwith disoditate. tate hot or mite. p p um phoscold. phate.

Lake water Heavy precipi- Heavy preci i- Sli ht reci i with sodium tate. tate hot r t te. p carbonate. cold.

Other dyestuffs, which normally react with the salts present in water and r'esponsible'for 1ts hardness; iform insoluble lakes, give improved resi'il s similar to the above when 'sodiumpyrophosphate is employed.

In the following examples are illustrated the actual use of the pyrophosphate salts both by grinding with the dyestuif and by previously adding to-the water of the dyebath before adding the dyestufis. In all examples the lake Water employed had a hardness corresponding to parts per million.

Eaaamplev I 0.2 parts of direct fast yellow 5Gv (concen-' trated) are milled with 0.098 parts of anhydrous sodium pyrophosphate. 200 parts of lake water are added and the wholeis brought to the boiling temperature. The dyestufi is practically completely in solution at boiling temperature. After cooling and standing overnight, some of the dyestuif precipitates out in the form of a gel with no evidence of the formation of a lake. Cotton may be dyed yellow from the above bath in clear clean shades.

. Example I I To 200 parts of lake water are added 0.098 parts of anhydrous sodium pyrophosphate. The solution'is heated to the boiling point and there are then added 0.2 parts of direct fast yellow 5G (concentrated). The results further known that the concentration of p rophosphate used may be varied and that in general the higher the degree of hardness present in the water, the greater willbe the amount of pyrophosphate salt necessary to give good results. y

We are aware of the fact that the pyrophosphate salt may be mixed with the dye- Stufi". in any convenient step in the preparatlon of the dyestuff itself, as for example, previ-' 3 ous to the drying and milling. It is also known to us that the pyrophosphate salts may likewise be used to advantage for the purposes set forth, in combination with other salts as for example disodium phosphate, so-

dium carbonate, sodium sulphate and the like.-

. We thereforedo not purpose limiting the patent granted hereon other than as necessitated by the priorart. 1 1

We claim as our invention:

a 1. The process of improving the solubilit of water soluble dyestuffs in water, whic comprises dissolving the dyestuff in water in the presence of a soluble pyrophosphate salt.

2. The process of improving the solubility i of water soluble. dyestufl's' in water, which comprises dissolving the dyestuff in waterin the presence of'sodium pyrophosphate.

3. The process of rendering water soluble dyestuffs more completely soluble-: in' hard' 0 subscribed our names at waters, which comprises adding to the hard waters a soluble pyrophosphate salt and a dyestufi.

4. The process of rendering water soluble dyestufls more completely soluble in hard waters, which comprises adding to the hard watars sodium pyrophosphate and a dyestu 5. As a new article of manufacture, water soluble dyestufi' material containing a soluble pyrophosphate.

6. As a new'article of manufacture; water soluble dyestufl material containing sodium pyrophosphate.

dyestufi and sodium pyrophosphate.

In testimony whereof we have hereunto Carrollville, Wis, February 3, 1928.

ARTHUR R. MURPHY. JOSEPHB. OESCH.

Solutions containing a water soluble 1 dyestufi' and a soluble pyrophosphate salt.

8. Solutions containing a. water soluble 

